The long-term objective of this research is to discover how bilingual children who use cochlear implants acquire the phonological systems of their target languages, and a critical problem is that our fundamental understanding of speech development in bilingual children with hearing loss is extremely limited. Bilingual children living in the US are at risk for not receiving appropriate diagnostic and intervention speech and language services; a health care issue that is even more critical for bilingual children who are cochlear implant users. Results from this study will help clinicians make more informed decisions regarding the assessment and treatment of the speech and language of bilingual children with cochlear implants by providing empirical data on speech acquisition. The goals of the proposed project will be met via comprehensive analyses of the phonological systems of bilingual children with cochlear implants and through comparisons to bilingual children with normal hearing and monolingual English-speaking children with cochlear implants. The study has two specific aims: (1) to investigate the effects of the diminished auditory signal by comparing the phonological skills of bilingual children with cochlear implants to those of their bilingual peers with normal hearing, and (2) to examine cross-language effects by comparing the phonological skills of bilingual children with cochlear implants to those of their monolingual English-speaking peers with cochlear implants. The aims will be addressed by conducting a comprehensive set of analyses to investigate speech acquisition in bilingual children who use cochlear implants and compare them to their bilingual peers with normal hearing and their monolingual peers with cochlear implants. General measures of phonology, specific analyses of speech, and measures of auditory comprehension and speech perception will be used to compare the performance of the groups of children. The analyses include measures that have been used with monolingual children with cochlear implants (such as segmental accuracy) as well as analyses that are novel for the target population of bilingual children with cochlear implants (e.g., phonological whole-word measures). Research on speech development in bilingual children with cochlear implants is limited, and comprehensive analyses of the phonological skills involving the same population are virtually non-existent. Moreover, research on bilingual language development in children with cochlear implants presents conflicting information regarding whether or not to recommend using both languages. The proposed study will address both of these issues, filling a critical gap in knowledge that currently acts as a barrier to progress in the field by laying the groundwork on speech development in bilingual children with cochlear implants. Furthermore, the results of the proposed research will also have an impact on clinical practice by providing information regarding the development of phonological systems in bilingual children who use cochlear implants.